This invention relates to charge coupled device imager video outputs, and more specifically to a method for correcting those output signals which are generated by defective cells in the CCD imager.
Recently, much effort has been devoted to the advancement of the field of image sensing devices. Self-scanned charge transfer arrays, both charge-coupled and bucket-brigade types, and X, Y addressed photo-diode arrays have been the object of much of this effort. One of the barriers to low cost production of these imager chips is the presence of defective individual cells in the array. The signal from a defective cell will differ greatly from a properly functioning cell, and when processed and displayed, will be evident.
Since large arrays are commercially desirable, but not feasible at a competitive price, other alternatives to solve the problem of less than 100% yields were investigated. One approach to the solution of the problem is given in U.S. Pat. No. 3,904,818. In this patent, the problem addressed is that of "white video defects". The white video defects are said to be caused by dark current spikes, and removal of the signals caused by the spikes is taken care of by an algorithm which replaces any defect signal with a signal equal to the average of the signals adjacent to the defect signal. A significant problem with this method is that of delay. Signals must be delayed two clock cycles in order to accomplish the averaging process and replace a defect signal.